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Cell Communciation
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  • NO – local regulator – help with relaxation of smooth muscles – viagra – allows for erection of penis – if released by endothelial cells Can act as a neurotransmitter if released by neurons; kills backter and cancer cells if secreted by WBC

Cell Communciation Presentation Transcript

  • 1. Cell Communication
  • 2. Cell “signaling”
    • Direct communication between cells
      • Cell junctions between adjacent cells
      • Cell-cell recognition through interaction of surface protein
    • Communication via signals between cells (signal transduction pathways)
      • Local signaling
      • Long distance signaling
  • 3. Direct Communication
    • Gap junctions & Plasmodesmata
      • Results in cytoplasmic continuity favoring cellular interactions
  • 4. Direct Communication
    •   Cell surface contacts
      • Receptor protein specificity
  • 5. Direct Communication: Surface Proteins - Yeast Cells
    • Mating in yeast cells
    • a cell
      • Releases a-factor that binds to  cell receptors
    •  cell
      • Releases  -factor that binds to a cell receptors
    • Results
      • Fusion of 2 cells (mating) producing diploid cell
  • 6. Direct Communication: Surface Proteins - Yeast Cells
  • 7. Signal Transduction Pathways
    • Local communication
      • “Transmitting cell” secretes a local regulator (molecule that “talks” only to cells close by)
    • Long Distance communication
      • “Transmitting cell” secretes a molecule that travels long distances to reach its target cell
  • 8. Local Communication
    • Paracrine Signaling
      • Cell secretes a molecule that interacts with a target cell nearby
    • Synaptic Signaling
      • Cell releases a neurotransmitter into a synapse between two cells that are nearly touching
  • 9. Long Distance Communication
    • Endocrine signaling
      • Specialized cells release molecules (hormones) via blood stream
      • Hormones move to distant target cells to elicit response
  • 10.  
  • 11. Signal Transduction Pathway
  • 12. 3 Steps in Signal Transduction
    • Reception of the signal
    • Transduction of the message to the intended “receiver”
    • Response to the message
  • 13. Signal Reception
    • Lock-&-key analogy (enzyme-substrate recognition)
    • Ligand molecules (Signal molecule) interacts with receptor protein
      • Receptor protein bound in the plasma membrane
    • Conformational change of ligand-receptor causes activation
  • 14. Examples of membrane associated receptor molecules
    • G-Protein linked receptors
    • Tyrosine-kinase receptors
    • Ion-channel receptors
    • Exception
      • Intracellular receptors
  • 15. G-Protein linked Receptors
    • Functions
      • Embryonic development
      • Vision and smell sensory reception
      • Bacterial infections
  • 16.
    • G-protein acts as the ON-OFF switch
    • Inactive form when bound to GDP
    • Active form when bound to GTP
  • 17. Tyrosine-kinase Receptors
    • Function
      • Receives “growth factor” signals that stimulate cell division
      • Uncontrolled cell growth - cancer
  • 18.
    • Inactive form – Exists as single polypeptides
    • Active form – Formation of a dimer that acts as an enzyme and its own substrate
  • 19. Ion-channel Receptors
    • Important in the nervous system
  • 20. Exception
    • Intracellular Receptors
      • Signals able to pass through the plasma membrane
      • Small molecule (NO) or lipid soluble (testosterone)
        • Nitric oxide
          • Relax smooth muscle
          • Act as a neurotransmitter
          • Help kill unwanted cells
  • 21.  
  • 22. Signal Transduction
    • Enzyme Cascade
    • Second Messengers
    • Amplification
      • Multi-step pathway to turn “on” many different target molecules
      • More steps involved = more activated products
  • 23. Signal Transduction
    • Domino Effect
    • Enzyme Cascade
      • Protein phosphorylation
        • Protein kinase
          • Adds phosphates to substrate from ATP
        • Protein phosphatase
          • Removes phosphates from substrate
  • 24. Enzyme Cascade
  • 25.
    • Gene Activation
  • 26. Second Messengers
    • “ Activated relay molecule”
    • Participate in G-protein linked receptors & tyrosine-kinase receptor
    • Types
      • cyclic AMP
      • Calcium ions
      • DAG (Diacylglycerol)
      • IP3 (Inositol triphosphate)
  • 27. G-protein & cAMP
    • Epinephrine & glycogen breakdown
  • 28. Calcium ions
    • Muscle Contraction
    • Neurotransmitter release
  • 29.  
  • 30. Cellular Response
    • Cellular activity/metabolism
    • Rearrangement of cytoskeleton (movement)
    • Specific gene activity
    • Synthesis of enzymes or regulate the activity of an enzyme
  • 31.